Optimization of persistent state storage in cookies

In my project I have two large datatables which save its state in cookies. Average size of data to store is about 1500-2000 bytes. Saving state of one table cause cookie expiration of another due to 4 KiB limit. In current implementation, old cookies are expired in order of creation time. I think that it is necessary to expire cookie of current table at first if exists.

Here is a path.

@@ -4517,6 +4517,7 @@
 			
 			if ( iNewCookieLen+document.cookie.length+10 > 4096 ) /* Magic 10 for padding */
 			{
+				var equalCookieIdx = -1;
 				for ( var i=0, iLen=aCookies.length ; i<iLen ; i++ )
 				{
 					if ( aCookies[i].indexOf( sBaseName ) != -1 )
@@ -4532,10 +4533,28
 									"name": aSplitCookie[0],
 									"time": oData.iCreate
 								} );
+								
+								var cookieName = aSplitCookie[0];
+								while (cookieName.charAt(0)==' ')
+								{
+									cookieName = cookieName.substring(1, cookieName.length);
+								}
+								if (cookieName == sNameFile)
+								{
+									equalCookieIdx = aOldCookies.length - 1;
+								}
 							}
 						}
 						catch( e ) {}
-					}
+					}
+				}
+				// At first delete cookie with equal name if exists
+				if ( equalCookieIdx >= 0 )
+				{
+					var old = aOldCookies[equalCookieIdx];
+					document.cookie = old.name+"=; expires=Thu, 01-Jan-1970 00:00:01 GMT; path="+
+						aParts.join('/') + "/";
+					aOldCookies.splice(equalCookieIdx, 0);
 				}
 		
 				// Make sure we delete the oldest ones first